SMOOTH EXCIMER-LASER CORONARY ANGIOPLASTY (SELCA) AND CONVENTIONAL EXCIMER-LASER ANGIOPLASTY - COMPARISON OF VASCULAR INJURY AND SMOOTH-MUSCLE CELL-PROLIFERATION

Although the excimer laser, which utilizes 'non-thermal ablation effec ts', has achieved encouraging results in early clinical trials, the lo ng-term results have failed to show any advantage over conventional pe rcutaneous transluminal coronary angioplasty (PTCA). A new system, Smo oth Excimer Laser Coronary Angioplasty (SELCA), has been developed to reduce the tissue damage in the vessel wall caused by shock waves and vapour bubbles. SELCA (wavelength 308 nm, pulse duration 115 ns, repet ition rate 150 Hz and energy density 50 mJ mm(-2)) lowers the amount o f shock wave formation and pressure peak amplitude in the surrounding tissue by about eight times when compared to the conventional 308 nm e xcimer laser (ELCA). In this preclinical evaluation, this new system w as compared to ELCA. Fifty New Zealand White rabbits were stimulated b y repeated weak DC impulses for a period of 28 days in order to form a n atherosclerotic plaque in the right carotid artery. The vessels were excised 3, 7, 14 and 28 days after laser irradiation for immunohistoc hemical analysis. SELCA and ELCA laser treatment lead to a decrease in maximal intimal wall thickness 3 days after intervention (control: 17 7 +/- 4 mu m; SELCA: 131 +/- 22 mu m; ELCA: 120 +/- 33 mu m). In the p eriod between 3 and 28 days, a moderate increase in intimal wall thick ness was observed after SELCA treatment compared to a significant incr ease after ELCA (28 days after intervention: SELCA: 157 +/- 22 mu m; E LCA: 274 +/- 28 mu m). Bromodeoxyuridine (BrdU) was applied 18 and 12h before excision of the vessels in order to determine the percent of c ells undergoing DNA synthesis. The percent of BrdU labelled SMC in the intima (control: 13 +/- 2 cells mm(-2)) increased in both groups afte r 3 days (SELCA: 248 +/- 107 cells mm(-2); ELCA: 162 +/- 41 cells mm(- 2)) and 7 days (SELCA: 162 +/- 55 cells mm(-2); ELCA: 279 +/- 119 cell s mm(-2)). The present results demonstrate that vascular wall injury a nd increase in intimal wall thickness following SELCA are reduced in c omparison to the results achieved with the conventional technique. Fur ther trials are necessary to assess whether these improvements will le ad to more favourable long-term results after excimer laser angioplast y.